Proton electrolyte membranes have been studied in many years, but the existing membranes are still inadequate in performance for many applications. Polymer proton conductors, such as perfluorosulfonic polymers (such as Nafion), have good chemical, electrochemical and mechanical stability, but they have serious disadvantages, such as low proton conductivity at low humidity and high temperature, dimensional changes with water contents, poor hydrophilicity, large amount of fuel crossover, and high cost. The fuel cells with these conventional PEMs as the electrolytes can be operated usually below 80° C.
However, to date, conventional hybrid inorganic-organic proton conducting membranes do not have adequate thermal stability to be used above 120° C., especially when the membranes have —SO3H groups.
Conventional polymer chemistry techniques are disclosed in U.S. Pat. No. 3,408,420 to Wiggill, U.S. Pat. No. 4,707,517 to Bullen et al., U.S. Pat. No. 5,389,726 to Sojka, U.S. Pat. No. 5,453,467 to Bamford et al., U.S. Pat. No. 5,840,800 to Joffre et al., U.S. Pat. No. 6,201,064 to Aoyama et al., and U.S. Pat. No. 6,719,920 to Arhart et al.; U.S. Pat. App. Pub. No. 2002/0127474 to Fleischer et al.; and Int. Pat. App. Pub. No. WO04/005380 to Oren et al. Techniques disclosed in the above mentioned patents and publications can be adapted for use in preparing materials according to the present invention.